1. Technical Field
Example embodiments of the present invention relate in general to technology of cancelling interference of a wireless communication system, and more particularly, to a method of cancelling inter-subcarrier interference in a distributed antenna system capable of effectively cancelling inter-subcarrier interference in a frequency selective fading environment, and an apparatus for performing the same.
2. Related Art
According to rapid developments of a wireless communication system, demands for transmitting and receiving massive information at high speed are being increased. In order to satisfy the demands, a method of additionally installing a plurality of distributed antennas in conventional cell coverage and performing cooperative communication among a plurality of transmitters and receivers which are geographically distributed is being used.
The distributed antenna system can eliminate a shade area, reduce transmission power, and improve characteristics of bandwidth versus transmission efficiency, and particularly, a system using a relay node connected to a base station through an optical cable as an distributed antenna has advantages in resource allocation of high efficiency and cooperative signal transmission between distributed antennas since an additional wireless resource is not required for transmitting and receiving a control signal.
Meanwhile, according to developments of semiconductor technology, it is possible to transmit by converting high speed data into low speed data as it is possible to implement a circuit for processing a lot of subcarriers in one integrated circuit. As a calculation is more simplified by using fast Fourier transform (FFT) signal processing technology, an orthogonal frequency division multiplexing (OFDM) method is being used in various commercial wireless and mobile communication systems.
The wireless communication methods using the OFDM transmit a signal using flat channel characteristics even in a wireless environment having frequency selective fading channel characteristics by using multiple subcarriers. Efficiency of bandwidth and a data transmission rate can be improved by using the OFDM characteristics, a modulation and demodulation method can be flexibly applied according to a state of each of a plurality of channels, and data resources which are separated can be multiplexed.
However, since the OFDM uses orthogonal characteristics among a plurality of subcarriers, the OFDM has very sensitive characteristics in inter-subcarrier synchronization. Particularly, in the wireless communication environment using a plurality of transmission points (or nodes) such as the distributed antenna system or the cooperative communication system, there is a problem in which performance is severely degraded when there is an error in the inter-subcarrier synchronization.
On the other hand, recently, use of an Alamouti coded OFGM method which obtains a transmission antenna diversity gain using an Alamouti code has been considered for the distributed antenna system. In order to maximize the diversity gain in the distributed antenna system, the inter-subcarrier interference generated due to a frequency error has to be decreased.
In order to satisfy the requirements described above, studies for reducing the inter-subcarrier interference in the wireless communication system using the OFDM are in progress. However, there is a problem in which performance is degraded when applied to the frequency selective fading channel environment since the studies for reducing the inter-subcarrier interference which are currently in progress have a premise of the wireless channel environment having flat fading characteristics.